add_node · Flowchart MCP: Risk & Policy

WHAT IT DOES

What add_node does on Flowchart MCP

AI agents use add_node to create or update resources in Flowchart MCP — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Flowchart MCP environment.

WHY IT NEEDS A POLICY

Why add_node needs a policy

Adding a node to a flowchart creates or modifies diagram data but is reversible and has no external side effects. This is a standard Write operation. Severity is low because the blast radius of misuse is limited to the diagram itself with no system impact or data destruction.

From the tool's definition Tool name 'add_node' combined with server description stating '14 MCP tools for full node/edge CRUD' and 'create, edit, and export flowcharts' indicates this creates a new element in a diagram. The action is reversible (node can be removed via remove_node).

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

add_node Rate-limited

add_node stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "add_node": {
      "limits": [
        {
          "counter": "add_node_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches Flowchart MCP, so you can run agents against it safely.

FAQ

Questions about add_node

What does the add_node tool do? +

Add a node to the flowchart. It is categorised as a Write tool in the Flowchart MCP MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on add_node? +

Register the Flowchart MCP server in PolicyLayer and add a rule for add_node: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Flowchart MCP. Nothing to install.

What risk level is add_node? +

add_node is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit add_node? +

Yes. Add a rate_limit block to the add_node rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.

How do I block add_node completely? +

Set action: deny in the PolicyLayer policy for add_node. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.

What MCP server provides add_node? +

add_node is provided by the Flowchart MCP server (zafer-liu/flowchart_mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.